Allow projectiles to penetrate through ships, dealing damage multiple times

source/CollisionSet.cpp

@@ -23,7 +23,6 @@ PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 #include <algorithm>
 #include <cstdlib>
 #include <numeric>
-#include <set>
 #include <string>
 
 using namespace std;
@@ -127,23 +126,23 @@ void CollisionSet::Finish()
 
 // Get the first object that collides with the given projectile. If a
 // "closest hit" value is given, update that value.
-Body *CollisionSet::Line(const Projectile &projectile, double *closestHit) const
+Body *CollisionSet::Line(const Projectile &projectile, double *closestHit, const set<const Body *> *hits) const
 {
 	// What objects the projectile hits depends on its government.
 	const Government *pGov = projectile.GetGovernment();
 
 	// Convert the start and end coordinates to integers.
 	Point from = projectile.Position();
 	Point to = from + projectile.Velocity();
-	return Line(from, to, closestHit, pGov, projectile.Target());
+	return Line(from, to, closestHit, hits, pGov, projectile.Target());
 }
 
 
 
 // Check for collisions with a line, which may be a projectile's current
 // position or its entire expected trajectory (for the auto-firing AI).
 Body *CollisionSet::Line(const Point &from, const Point &to, double *closestHit,
-		const Government *pGov, const Body *target) const
+		const set<const Body *> *hits, const Government *pGov, const Body *target) const
 {
 	int x = from.X();
 	int y = from.Y();
@@ -179,8 +178,10 @@ Body *CollisionSet::Line(const Point &from, const Point &to, double *closestHit,
 
 			// Check if this projectile can hit this object. If either the
 			// projectile or the object has no government, it will always hit.
+			// If this projectile has already hit this object, it won't hit it again.
 			const Government *iGov = it->body->GetGovernment();
-			if(it->body != target && iGov && pGov && !iGov->IsEnemy(pGov))
+			if((it->body != target && iGov && pGov && !iGov->IsEnemy(pGov))
+					|| (hits && hits->count(it->body)))
 				continue;
 
 			const Mask &mask = it->body->GetMask(step);
@@ -208,7 +209,7 @@ Body *CollisionSet::Line(const Point &from, const Point &to, double *closestHit,
 			warned = true;
 		}
 		Point newEnd = from + pVelocity.Unit() * USED_MAX_VELOCITY;
-		return Line(from, newEnd, closestHit, pGov, target);
+		return Line(from, newEnd, closestHit, hits, pGov, target);
 	}
 
 	// When stepping from one grid cell to the next, we'll go in this direction.
@@ -253,8 +254,10 @@ Body *CollisionSet::Line(const Point &from, const Point &to, double *closestHit,
 
 			// Check if this projectile can hit this object. If either the
 			// projectile or the object has no government, it will always hit.
+			// If this projectile has already hit this object, it won't hit it again.
 			const Government *iGov = it->body->GetGovernment();
-			if(it->body != target && iGov && pGov && !iGov->IsEnemy(pGov))
+			if((it->body != target && iGov && pGov && !iGov->IsEnemy(pGov))
+					|| (hits && hits->count(it->body)))
 				continue;
 
 			const Mask &mask = it->body->GetMask(step);

source/CollisionSet.h

@@ -13,6 +13,7 @@ PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 #ifndef COLLISION_SET_H_
 #define COLLISION_SET_H_
 
+#include <set>
 #include <vector>
 
 class Government;
@@ -41,11 +42,11 @@ class CollisionSet {
 
 	// Get the first object that collides with the given projectile. If a
 	// "closest hit" value is given, update that value.
-	Body *Line(const Projectile &projectile, double *closestHit = nullptr) const;
+	Body *Line(const Projectile &projectile, double *closestHit = nullptr, const std::set<const Body *> *hits = nullptr) const;
 	// Check for collisions with a line, which may be a projectile's current
 	// position or its entire expected trajectory (for the auto-firing AI).
 	Body *Line(const Point &from, const Point &to, double *closestHit = nullptr,
-		const Government *pGov = nullptr, const Body *target = nullptr) const;
+		const std::set<const Body *> *hits = nullptr, const Government *pGov = nullptr, const Body *target = nullptr) const;
 
 	// Get all objects within the given range of the given point.
 	const std::vector<Body *> &Circle(const Point &center, double radius) const;

source/Engine.cpp

@@ -1931,112 +1931,129 @@ void Engine::HandleMouseClicks()
 // this is multi-threaded in the future, that will need to change.
 void Engine::DoCollisions(Projectile &projectile)
 {
-	// The asteroids can collide with projectiles, the same as any other
-	// object. If the asteroid turns out to be closer than the ship, it
-	// shields the ship (unless the projectile has a blast radius).
-	Point hitVelocity;
-	double closestHit = 1.;
-	shared_ptr<Ship> hit;
 	const Government *gov = projectile.GetGovernment();
-
-	// If this "projectile" is a ship explosion, it always explodes.
-	if(!gov)
-		closestHit = 0.;
-	else if(projectile.GetWeapon().IsPhasing() && projectile.Target())
-	{
-		// "Phasing" projectiles that have a target will never hit any other ship.
-		shared_ptr<Ship> target = projectile.TargetPtr();
-		if(target)
+	// Keep track of which ships this projectile has directly impacted this frame.
+	set<const Body *> hits;
+	bool hasHit = true;
+	while(!projectile.IsDead() && hasHit)
+	{
+		// The asteroids can collide with projectiles, the same as any other
+		// object. If the asteroid turns out to be closer than the ship, it
+		// shields the ship (unless the projectile has a blast radius).
+		double closestHit = 1.;
+		shared_ptr<Ship> hit;
+		Point hitVelocity;
+		hasHit = false;
+
+		// If this "projectile" is a ship explosion, it always explodes.
+		if(!gov)
+			closestHit = 0.;
+		else if(projectile.GetWeapon().IsPhasing() && projectile.Target())
 		{
-			Point offset = projectile.Position() - target->Position();
-			double range = target->GetMask(step).Collide(offset, projectile.Velocity(), target->Facing());
-			if(range < 1.)
+			// "Phasing" projectiles that have a target will never hit any other ship.
+			shared_ptr<Ship> target = projectile.TargetPtr();
+			if(target)
 			{
-				closestHit = range;
-				hit = target;
-			}
-		}
-	}
-	else
-	{
-		// For weapons with a trigger radius, check if any detectable object will set it off.
-		double triggerRadius = projectile.GetWeapon().TriggerRadius();
-		if(triggerRadius)
-			for(const Body *body : shipCollisions.Circle(projectile.Position(), triggerRadius))
-				if(body == projectile.Target() || (gov->IsEnemy(body->GetGovernment())
-						&& reinterpret_cast<const Ship *>(body)->Cloaking() < 1.))
+				Point offset = projectile.Position() - target->Position();
+				double range = target->GetMask(step).Collide(offset, projectile.Velocity(), target->Facing());
+				if(range < 1.)
 				{
-					closestHit = 0.;
-					break;
+					closestHit = range;
+					hit = target;
 				}
-
-		// If nothing triggered the projectile, check for collisions with ships.
-		if(closestHit > 0.)
-		{
-			Ship *ship = reinterpret_cast<Ship *>(shipCollisions.Line(projectile, &closestHit));
-			if(ship)
-			{
-				hit = ship->shared_from_this();
-				hitVelocity = ship->Velocity();
 			}
 		}
-		// "Phasing" projectiles can pass through asteroids. For all other
-		// projectiles, check if they've hit an asteroid that is closer than any
-		// ship that they have hit.
-		if(!projectile.GetWeapon().IsPhasing())
+		else
 		{
-			Body *asteroid = asteroids.Collide(projectile, &closestHit);
-			if(asteroid)
+			// For weapons with a trigger radius, check if any detectable object will set it off.
+			double triggerRadius = projectile.GetWeapon().TriggerRadius();
+			if(triggerRadius)
+				for(const Body *body : shipCollisions.Circle(projectile.Position(), triggerRadius))
+					if(body == projectile.Target() || (gov->IsEnemy(body->GetGovernment())
+							&& reinterpret_cast<const Ship *>(body)->Cloaking() < 1.))
+					{
+						closestHit = 0.;
+						break;
+					}
+
+			// If nothing triggered the projectile, check for collisions with ships.
+			if(closestHit > 0.)
 			{
-				hitVelocity = asteroid->Velocity();
-				hit.reset();
+				Ship *ship = reinterpret_cast<Ship *>(shipCollisions.Line(projectile, &closestHit, &hits));
+				if(ship)
+				{
+					hit = ship->shared_from_this();
+					hitVelocity = ship->Velocity();
+					// Only record direct hits. Phasing projectiles or projectiles
+					// that were set off by their trigger radius don't need to
+					// check for multiple collisions in a single frame.
+					hasHit = true;
+				}
+			}
+			// "Phasing" projectiles can pass through asteroids. For all other
+			// projectiles, check if they've hit an asteroid that is closer than any
+			// ship that they have hit.
+			if(!projectile.GetWeapon().IsPhasing())
+			{
+				Body *asteroid = asteroids.Collide(projectile, &closestHit);
+				if(asteroid)
+				{
+					hitVelocity = asteroid->Velocity();
+					hit.reset();
+					// Projectiles always die when impacting an asteroid.
+					projectile.Kill();
+				}
 			}
 		}
-	}
-
-	// Check if the projectile hit something.
-	if(closestHit < 1.)
-	{
-		// Create the explosion the given distance along the projectile's
-		// motion path for this step.
-		projectile.Explode(visuals, closestHit, hitVelocity);
 
-		// If this projectile has a blast radius, find all ships within its
-		// radius. Otherwise, only one is damaged.
-		double blastRadius = projectile.GetWeapon().BlastRadius();
-		bool isSafe = projectile.GetWeapon().IsSafe();
-		if(blastRadius)
+		// Check if the projectile hit something.
+		if(closestHit < 1.)
 		{
-			// Even friendly ships can be hit by the blast, unless it is a
-			// "safe" weapon.
-			Point hitPos = projectile.Position() + closestHit * projectile.Velocity();
-			for(Body *body : shipCollisions.Circle(hitPos, blastRadius))
+			// Create the explosion the given distance along the projectile's
+			// motion path for this step.
+			projectile.Explode(visuals, closestHit, hitVelocity);
+
+			// If this projectile has a blast radius, find all ships within its
+			// radius. Otherwise, only one is damaged.
+			double blastRadius = projectile.GetWeapon().BlastRadius();
+			bool isSafe = projectile.GetWeapon().IsSafe();
+			if(blastRadius)
 			{
-				Ship *ship = reinterpret_cast<Ship *>(body);
-				if(isSafe && projectile.Target() != ship && !gov->IsEnemy(ship->GetGovernment()))
-					continue;
-
-				int eventType = ship->TakeDamage(visuals, projectile.GetWeapon(), 1.,
-					projectile.DistanceTraveled(), projectile.Position(), projectile.GetGovernment(), ship != hit.get());
+				// Even friendly ships can be hit by the blast, unless it is a
+				// "safe" weapon.
+				Point hitPos = projectile.Position() + closestHit * projectile.Velocity();
+				for(Body *body : shipCollisions.Circle(hitPos, blastRadius))
+				{
+					Ship *ship = reinterpret_cast<Ship *>(body);
+					if(isSafe && projectile.Target() != ship && !gov->IsEnemy(ship->GetGovernment()))
+						continue;
+
+					int eventType = ship->TakeDamage(visuals, projectile.GetWeapon(), 1.,
+						projectile.DistanceTraveled(), projectile.Position(), projectile.GetGovernment(), ship != hit.get());
+					if(eventType)
+						eventQueue.emplace_back(gov, ship->shared_from_this(), eventType);
+				}
+			}
+			else if(hit)
+			{
+				int eventType = hit->TakeDamage(visuals, projectile.GetWeapon(), 1.,
+					projectile.DistanceTraveled(), projectile.Position(), projectile.GetGovernment());
 				if(eventType)
-					eventQueue.emplace_back(gov, ship->shared_from_this(), eventType);
+					eventQueue.emplace_back(gov, hit, eventType);
+			}
+
+			if(hit)
+			{
+				DoGrudge(hit, gov);
+				hits.insert(hit.get());
 			}
 		}
-		else if(hit)
-		{
-			int eventType = hit->TakeDamage(visuals, projectile.GetWeapon(), 1.,
-				projectile.DistanceTraveled(), projectile.Position(), projectile.GetGovernment());
-			if(eventType)
-				eventQueue.emplace_back(gov, hit, eventType);
-		}
-
-		if(hit)
-			DoGrudge(hit, gov);
 	}
-	else if(projectile.MissileStrength())
+
+	// If the projectile is still alive, give the anti-missile systems
+	// a chance to shoot it down.
+	if(!projectile.IsDead() && projectile.MissileStrength())
 	{
-		// If the projectile did not hit anything, give the anti-missile systems
-		// a chance to shoot it down.
 		for(Ship *ship : hasAntiMissile)
 			if(ship == projectile.Target() || gov->IsEnemy(ship->GetGovernment()))
 				if(ship->FireAntiMissile(projectile, visuals))

source/Projectile.cpp

@@ -258,17 +258,20 @@ void Projectile::Move(vector<Visual> &visuals, vector<Projectile> &projectiles)
 
 
 // This projectile hit something. Create the explosion, if any. This also
-// marks the projectile as needing deletion.
+// marks the projectile as needing deletion if it has run out of penetrations.
 void Projectile::Explode(vector<Visual> &visuals, double intersection, Point hitVelocity)
 {
-	clip = intersection;
 	distanceTraveled += velocity.Length() * intersection;
 	for(const auto &it : weapon->HitEffects())
 		for(int i = 0; i < it.second; ++i)
 		{
 			visuals.emplace_back(*it.first, position + velocity * intersection, velocity, angle, hitVelocity);
 		}
-	lifetime = -100;
+	if(++penetrations > weapon->Penetration())
+	{
+		clip = intersection;
+		lifetime = -100;
+	}
 }
 
 
@@ -281,10 +284,19 @@ double Projectile::Clip() const
 
 
 
+// Get whether the lifetime on this projectile has run out.
+bool Projectile::IsDead() const
+{
+	return lifetime < 0;
+}
+
+
+
 // This projectile was killed, e.g. by an anti-missile system.
 void Projectile::Kill()
 {
 	lifetime = 0;
+	penetrations = weapon->Penetration();
 }
 
 

source/Projectile.h

@@ -53,10 +53,12 @@ class Projectile : public Body {
 	// Move the projectile. It may create effects or submunitions.
 	void Move(std::vector<Visual> &visuals, std::vector<Projectile> &projectiles);
 	// This projectile hit something. Create the explosion, if any. This also
-	// marks the projectile as needing deletion.
+	// marks the projectile as needing deletion if it has run out of penetrations.
 	void Explode(std::vector<Visual> &visuals, double intersection, Point hitVelocity = Point());
 	// Get the amount of clipping that should be applied when drawing this projectile.
 	double Clip() const;
+	// Get whether the lifetime on this projectile has run out.
+	bool IsDead() const;
 	// This projectile was killed, e.g. by an anti-missile system.
 	void Kill();
 
@@ -90,7 +92,8 @@ class Projectile : public Body {
 
 	double clip = 1.;
 	int lifetime = 0;
-	double distanceTraveled = 0;
+	double distanceTraveled = 0.;
+	int penetrations = 0;
 	bool hasLock = true;
 };
 

source/Weapon.cpp

@@ -124,6 +124,8 @@ void Weapon::LoadWeapon(const DataNode &node)
 				missileStrength = max(0., value);
 			else if(key == "anti-missile")
 				antiMissile = max(0., value);
+			else if(key == "penetration")
+				penetration = max(0., value);
 			else if(key == "velocity")
 				velocity = value;
 			else if(key == "random velocity")